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/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** Contact: Nokia Corporation (qt-info@nokia.com)
**
** This file is part of the QtXmlPatterns module of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** No Commercial Usage
** This file contains pre-release code and may not be distributed.
** You may use this file in accordance with the terms and conditions
** contained in the Technology Preview License Agreement accompanying
** this package.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file. Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain
** additional rights. These rights are described in the Nokia Qt LGPL
** Exception version 1.1, included in the file LGPL_EXCEPTION.txt in this
** package.
**
** If you have questions regarding the use of this file, please contact
** Nokia at qt-info@nokia.com.
**
**
**
**
**
**
**
**
** $QT_END_LICENSE$
**
****************************************************************************/
//
// W A R N I N G
// -------------
//
// This file is not part of the Qt API. It exists purely as an
// implementation detail. This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.
#ifndef Patternist_ItemMappingIterator_H
#define Patternist_ItemMappingIterator_H
#include "qabstractxmlforwarditerator_p.h"
#include "qdynamiccontext_p.h"
QT_BEGIN_HEADER
QT_BEGIN_NAMESPACE
namespace QPatternist
{
/**
* @short Proxies another QAbstractXmlForwardIterator, and for each item, returns the
* Item returned from a mapping function.
*
* ItemMappingIterator is practical when the items in an QAbstractXmlForwardIterator needs to
* be translated to another sequence, while still doing it in a pipe-lined
* fashion.
*
* This is achieved by that ItemMappingIterator's constructor takes
* an instance of a class, that must have the following member:
*
* @code
* TResult::Ptr mapToItem(const TSource &item,
* const Context &context) const
* @endcode
*
* For each item in the QAbstractXmlForwardIterator ItemMappingIterator proxies, this function is
* called and its return value becomes the return value of the ItemMappingIterator. If the
* mapping function returns null, ItemMappingIterator maps the next item in the source sequence
* such that a contiguous sequence of items is returned.
*
* Declaring the mapToItem() function as inline, can be a good way to improve performance.
*
* @see SequenceMappingIterator
* @author Frans Englich <frans.englich@nokia.com>
* @ingroup Patternist_iterators
*/
template<typename TResult, typename TSource, typename TMapper, typename Context = DynamicContext::Ptr>
class ItemMappingIterator : public QAbstractXmlForwardIterator<TResult>
{
public:
/**
* Constructs an ItemMappingIterator.
*
* @param mapper the object that has the mapToItem() sequence.
* @param iterator the QAbstractXmlForwardIterator whose items should be mapped.
* @param context the context that will be passed to the map function.
* May be null.
*/
ItemMappingIterator(const TMapper &mapper,
const typename QAbstractXmlForwardIterator<TSource>::Ptr &iterator,
const Context &context) : m_mapper(mapper)
, m_it(iterator)
, m_context(context)
, m_position(0)
{
Q_ASSERT(mapper);
Q_ASSERT(iterator);
}
/**
* @returns the next item in the sequence, or
* @c null if the end have been reached.
*/
virtual TResult next()
{
const TSource sourceItem(m_it->next());
if(qIsForwardIteratorEnd(sourceItem))
{
m_current = TResult();
m_position = -1;
return TResult();
}
else
{
m_current = m_mapper->mapToItem(sourceItem, m_context);
if(qIsForwardIteratorEnd(m_current))
return next(); /* The mapper returned null, so continue with the next in the source. */
else
{
++m_position;
return m_current;
}
}
}
virtual TResult current() const
{
return m_current;
}
virtual xsInteger position() const
{
return m_position;
}
virtual typename QAbstractXmlForwardIterator<TResult>::Ptr copy() const
{
return typename QAbstractXmlForwardIterator<TResult>::Ptr
(new ItemMappingIterator<TResult, TSource, TMapper, Context>(m_mapper, m_it->copy(), m_context));
}
private:
const TMapper m_mapper;
const typename QAbstractXmlForwardIterator<TSource>::Ptr m_it;
const Context m_context;
TResult m_current;
xsInteger m_position;
};
/**
* @short An object generator for ItemMappingIterator.
*
* makeItemMappingIterator() is a convenience function for avoiding specifying
* the full template instantiation for ItemMappingIterator. Conceptually, it
* is identical to Qt's qMakePair().
*
* @relates ItemMappingIterator
*/
template<typename TResult, typename TSource, typename TMapper, typename Context>
static inline
typename QAbstractXmlForwardIterator<TResult>::Ptr
makeItemMappingIterator(const TMapper &mapper,
const QExplicitlySharedDataPointer<QAbstractXmlForwardIterator<TSource> > &source,
const Context &context)
{
return typename QAbstractXmlForwardIterator<TResult>::Ptr
(new ItemMappingIterator<TResult, TSource, TMapper, Context>(mapper, source, context));
}
}
QT_END_NAMESPACE
QT_END_HEADER
#endif
|
